What is Calpainopathy?
Calpainopathy (previously known as limb-girdle muscular dystrophy type 2A, or LGMD2A) is a spectrum of disorders that cause muscle breakdown (atrophy) and weakness. Calpainopathy is caused by harmful genetic changes (mutations) in the CAPN3 gene. The primary symptom is worsening (progressive) muscle weakness of the hip, shoulder, and abdomen. The rate at which the muscles weaken can vary greatly, but many experience weakness to a point where a wheelchair becomes necessary. Other features include enlarged calf muscles, shortening and hardening of muscles leading to rigid joints (contractures), curvature of the spine (scoliosis), and prominence (winging) of the shoulder blades. Calpainopathy does not affect intelligence or mental function. Some individuals with the disease can have a mild course where they do not show symptoms (asymptomatic), while others may have severe symptoms that can be fatal. Failure to get enough oxygen to the lungs (respiratory failure) is the most common cause of death. The symptoms of the disease can vary greatly from person to person (even among people in the same family). The age that symptoms begin is also quite varied, with some individuals showing muscle weakness beginning in childhood. The most common age of onset is in the early teens. Genetic testing cannot predict how severe individuals will be affected.
How common is Calpainopathy?
The exact prevalence of calpainopathy is difficult to determine because of the wide range of symptoms. The estimated prevalence of calpainopathy in the population is approximately 1 in 80,000 individuals. Calpainopathy is more common among individuals of French Reunion Island and Indiana Amish descent.
How is Calpainopathy treated?
There is no cure for calpainopathy. Physical therapy helps patients to retain muscle strength and mobility for as long as possible. Mobility aids, such as walkers, canes, braces, and wheelchairs, may become necessary. If muscle weakness begins to affect the ability to breathe, a machine that assists with breathing (a ventilator) may be needed. Cardiac surveillance is recommended, and those who develop heart problems will need to see a heart specialist (a cardiologist) for treatment. Some individuals may need surgery if they develop scoliosis or contractures.
What is the prognosis for an individual with Calpainopathy?
The outlook for a person with calpainopathy varies. Generally, the earlier symptoms begin, the faster they progress. Some people with the disease experience only mild symptoms and may have near-normal strength. Others with a mild course may remain able to walk for 30 years or more after symptoms appear. People with more severe disease typically may need to use a wheelchair as early as 10 years after their diagnosis. There is evidence that symptoms progress faster in males than in females.